1. Field of the Invention
The present invention relates to a variator arrangement for a continuously variable transmission, having a shaft, a variator disk connected in a rotationally fixed manner to the shaft and a support disk which is concentric with said variator disk and which is rigidly connected to the shaft, the variator disk having on the side facing away from the support disk a traction area for transmitting torque.
2. Description of the Related Art
Variator arrangements of this type are used in toroidal transmissions but also for example in CVT transmissions.
Toroidal transmissions have at least one variator with two variator disks. The disks have annular traction areas which face one another and which define a toroidal space. Rollers are arranged within the toroidal space and engage with the variator disks in order to transmit a torque from one variator disk to the other variator disk. Toroidal transmissions of this type are generally known.
In order to transmit torque, the variator disks in the prior art are normally connected to the shaft in the hub region in a positive manner by means of gear toothings.
The high axial contact forces, particularly during displacement of the rollers, cause high loading of the variator disks in the vicinity of the gear toothing. This may lead to excessive stresses and consequently cause failure.
Furthermore, the production of the gear toothings is costly, particularly since the variator disk material is normally a high strength antifriction bearing steel.
In order to be able to better absorb the high axial forces, a variator disk is often assigned a support disk which is arranged on the opposite side of the variator disk from the traction area. The support disk allows the variator disk to be of lower mass and weight and, as a result, costs are saved. The support disk is in this case normally connected to the shaft in a positive manner in the circumferential direction. This connection is possible by means of gear toothing, though the support disk may also be formed in one piece with the shaft.
Although it is also conceivable to connect the variator disk to the shaft by means of gear toothing in the hub region when using a support disk, it is however preferred for the torque to be transmitted from the variator disk to the shaft by means of the support disk.
This may generally occur by means of non-positive connection. This is because the high axial contact forces may be utilized for transferring torque given a suitable design of axial bearing surfaces on the support disk and on the variator disk. In this case, use is made of the steel/steel frictional coefficient in the bearing region.
The transmission of torque from the variator disk to the support disk may however also occur in a positive manner. In this case, it is generally conceivable to join the variator disk in a positive manner on to the hub region of the support disk. In order to reduce the tangential forces, it is however more for the torque to be transferred in the outer circumferential region of the support disk or of the variator disk.
Although it is likewise generally conceivable here to provide gear toothing in the outer circumferential region, it is however considered to be more to implement positively connecting elements such as spheres in corresponding radial recesses both of the support disk and of the variator disk.
These approaches have in common the fact that excessive stresses may occur on account of the notch effect in the region of the positive connection between the variator disk and support disk.
It is hence the object of the present invention to specify a variator arrangement in which a positive connection between the variator disk and the support disk is improved.